The mechanisms of allergen induced airway narrowing, during allergen induced early (ER) and late (LR) responses, and airway hyperresponsiveness were investigated in vivo using the ovalbumin (OA) sensitized Brown Norway (BN) rat. ER and LR were induced by aerosolized OA. The lungs were fixed using a quick-freezing technique to maintain the pathological alterations as close as possible to their in vivo conditions. The results from both morphologic and morphometric studies showed that during the ER and LR, airway narrowing was mainly caused by airway smooth muscle contraction, but not by airway wall thickening or mucus. These findings were supported by intravenous administration of Evans blue which was used as a measure of vascular leakage. The degree of airway narrowing during the early response was greater in the large intrapulmonary airways than in the small intrapulmonary airways. Airway narrowing during the late response was limited to the large intrapulmonary airways. These findings were closely related to the mast cell distribution which progressively increased from small to large intrapulmonary airways in normal BN rats. These findings suggests that mast cells may play an important role in both early or late responses. / In order to study structural mechanisms of airway hyperresponsiveness, increased airway responses to inhaled methacholine were induced by repeated inhalational challenge of sensitized BN rats with OA. Quantitation of airway smooth muscle, airway wall area and epithelial area demonstrated that increased airway hyperresponsiveness was associated with the increased amount of airway smooth muscle but not with airway wall thickening. There was a correlation between the quantity of airway smooth muscle in large airways and the change in airway hyperresponsiveness. Hence, it is possible that an altered quantity of airway smooth muscle is an important mechanical contributor to airway narrowing in human allergic asthma.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70170 |
| Date | January 1991 |
| Creators | Du, Tao |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Pathology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001215097, proquestno: AAINN67527, Theses scanned by UMI/ProQuest. |
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